Usual washing or cleaning agents on the market contain surfactants in order to remove dirt and spots. As a rule, combinations of multiple surfactants, in particular from the group of the anionic, nonionic, cationic, and amphoteric surfactants, are used in this context. These surfactants alone are often not capable of sufficiently removing dirt and spots, so that further adjuvants are employed in modern washing or cleaning agents. Among these further adjuvants are enzymes of various kinds such as proteases, amylases, cellulases, mannanases, pectate lyases. Further classes of enzyme are known to one skilled in the art. Because of their direct cleaning action, hydrolytic enzymes in particular, such as proteases, amylases, or lipases, are a constituent of numerous textile-cleaning or dishwashing agents.
The cleaning action, critical for the end user, of the enzymes employed in washing or cleaning agents is determined not only by the enzyme structure but also to a substantial degree by how those enzymes are formulated, and by their stabilization against environmental influences.
Enzymes having washing or cleaning activity are formulated in both solid and liquid form. The group of the solid enzyme preparations includes in particular the enzyme granulates, made up of multiple ingredients, which in turn are incorporated preferably into solid washing or cleaning agents. Liquid or gel-type washing or cleaning agents, in contrast thereto, often contain liquid enzyme preparations; the latter, unlike the enzyme granulates, are much less protected from external influences.
A number of different protective actions have been proposed in order to increase the stability of such enzyme-containing liquid washing or cleaning agents. German patent application DE 20 38 103 (Henkel), for example, teaches the stabilization of enzyme-containing dishwashing agents using saccharides, while European patent EP 636 170 B1 (Procter & Gamble) discloses propylene glycol for enzyme stabilization in liquid cleaning agents.
Polyols, in particular glycerol and 1,2-propylene glycol, are described in the existing art as reversible protease inhibitors. A corresponding technical disclosure is found, for example, in international application WO 02/08398 A2 (Genencor).
The stabilization of enzymes in aqueous cleaning agents using calcium salts such as calcium formate, calcium acetate, or calcium propionate is described by U.S. Pat. No. 4,318,818 (Procter & Gamble). In aqueous systems, however, in particular in manual dishwashing agents, salts of polyvalent cations such as calcium cations often result in turbidity during storage. This negative effect is intensified upon storage at low temperatures. The possible utilization concentrations are thereby limited, so that a sufficient enzyme-stabilizing effect cannot be guaranteed.
A second group of known stabilizers is constituted by borax, boric acid, boronic acids, or salts or esters thereof. To be mentioned thereamong are principally derivatives having aromatic groups, e.g. ortho-, meta-, or para-substituted phenylboronic acids, in particular 4-formylphenylboronic acid (4-FPBA), or the salts or esters of the aforesaid compounds. The latter compounds are disclosed as enzyme stabilizers, for example, in international patent application WO 96/41859 A1 (Novo Nordisk). Boric acids and boric acid derivatives, for example, nevertheless often have the disadvantage that they form undesired byproducts with other ingredients of a composition, in particular ingredients of washing or cleaning agents, so that they are no longer available in the relevant agents for the desired cleaning purpose, or even remain behind as a contaminant on the washed material. In addition, boric acids or borates are regarded as disadvantageous in environmental terms.
The methods discovered hitherto and described in the existing art for stabilizing enzymes are not usable in every cleaning-agent formulation depending on the chemical nature of the stabilizers, and are not always sufficient in terms of their stabilizing effect.
The object of the present Application was therefore to furnish an improved stabilizing agent for enzymes as well as an enzyme-containing washing or cleaning agent having elevated enzyme stability.
It has now been found that the disadvantages of the kind described above do not occur when a special calcium compound is used.
The subject matter of the invention is therefore the use of calcium nitrate in enzyme-containing washing or cleaning agents.
A further subject of the invention is enzyme-containing washing or cleaning agents that contain calcium nitrate.
A further subject of the invention is a method for manual or automatic cleaning of hard surfaces, in particular dishes, using an agent according to the present invention.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.